Conventionally, printing systems merely informed a user when the marking material was at a level too low to confidently print any further jobs. An example of such a system is disclosed in U.S. Pat. No. 4,961,088. The entire contents of U.S. Pat. No. 961,088 are hereby incorporated by reference.
As disclosed in U.S. Pat. No. 4,961,088, the conventional printing system uses a digital image generator to generate the image to be printed as an electronic pixel stream, which is tapped and sent to be both frequency or rate analyzed and also counted with a weighting factor assigned by the frequency analysis, to obtain a weighted pixel count. This provides a toner consumption estimate calculation which in turn can be subtracted from the (known) original amount of toner in the toner container to determine the remaining amount of toner and provide a signal indicating a low marking material condition.
In other words, U.S. Pat. No. 4,961,088 discloses that customer replaceable unit (CRU) a toner cartridge comes pre-filled with a specified (known constant) initial amount of toner. That number is stored as a weighted pixel count in a ROM, EPROM, or other non-volatile memory. As each page is printed, the pixel frequency is monitored for that page, and an estimation of the average image type is determined for that page. The number of pixels for page is then assigned a weight per pixel. This calculated toner amount is subtracted from the remaining balance of toner, and the new toner amount balance value is saved. The next page of pixels is then calculated and subtracted from this value. This process continues until the warning level for remaining toner is attained. The user is then alerted that the toner CRU is nearing it's "end-of-life" condition. The process continues until a calculated remaining toner amount of zero is attained, which should coincide with the toner cartridge being empty. That is, continuously subtracting calculated toner usage this way from the known initial installed toner amount until the balance amount reaches zero automatically gives an "out of toner" indication, without ever actually sensing or examining the toner container itself.
Other examples of conventional systems which have a low marking warning system are U.S. Pat. No. 5,283,613; U.S. Pat. No. 5,204,699; U.S. Pat. No. 5,204,698; U.S. Pat. No. 3,409,901; U.S. Pat. No. 4,847,659; U.S. Pat. No. 4,468,112; and U.S. Pat. No. 4,908,666. The entire contents of U.S. Pat. No. 5,283,613; U.S. Pat. No. 5,204,699; U.S. Pat. No. 5,204,698; U.S. Pat. No. 3,409,901; U.S. Pat. No. 4,847,659; U.S. Pat. No. 4,468,112; and U.S. Pat. No. 4,908,666 are hereby incorporated by reference.
One of the variables which is commonly encountered with an all in one toner or ink cartridge is that the customer prints documents with unknown amounts of area coverage. The print cartridge is purchased containing a finite amount of toner or ink and the customer is advised that the cartridge will deliver a certain number of prints at a certain area coverage; eg., for xerographic printers, this is commonly around 4,000 prints at a 6 percent area coverage. Since the customer is unaware of the area coverage which is to be utilized in specific jobs, the customer is really not aware of when a cartridge is about to be exhausted. Often the customer carries excess inventory to avoid being taken by surprise or else actually runs out of toner or ink. This situation is also true for standard toner or ink cartridges used in printers whether the printers produce black and white or color pages.
A problem associated with the conventional devices is that the user is only warned upon entering a low marking material condition and the user is not given an accurate prediction of the marking material depletion date of the marking material cartridge. More specifically, the conventional devices do not provide the user with a dynamic estimation as to the remaining life of the marking material cartridge so that the user can accurately plan the acquisition of new cartridges without having to have an undesirable amount of cartridges on hand in storage. Also, the user cannot accurately predict if a job can be completed without changing a marking material cartridge in the middle of the job.
In view of these problems, the present invention proposes a system which provides a user with information concerning the number of pages remaining in a marking material cartridge. The present invention also proposes a system which will predict a depletion date based on past job parameters so that a user can accurately plan future acquisitions of marking material cartridges.